One hundred and eleven Lib Dems who to stood for parliament on 7 May have put their names to the letter, which argues that the MP for Westmorland and Lonsdale is the best candidate to rebuild the party after it lost 48 of its 56 MPs.

“In government we achieved plenty, but at huge political cost to our party. The results of the election show the need for a liberal voice,” the letter reads. “That need has never been stronger: to stand up for the liberal values which our country holds dear – fairness, respect, inclusion and opportunity for all.”

The letter – signed by candidates including Christine Jardine, who stood against Alex Salmond in Gordon; Duncan Hames, the former MP for Chippenham; and Jo Swinson, the former equalities minister – points out that the party has signed up 13,000 new members since polling day.

“Only the Liberal Democrats can provide that voice, but to do so effectively we need as our next leader someone who is not only a committed liberal but who is also an outstanding campaigner and an inspirational leader, who will ensure the liberal case is heard loud and clear. Somebody who reconnects the Liberal Democrats with the public,” the letter says.

“We believe the person who best fits that description as we start the task of rebuilding our party is Tim Farron,” it concludes.

Clegg resigned after the party’s worst performance in a general election since it was formed from the merger of the Liberal party and the Social Democratic party in 1988.

The leadership contest is expected to come down to a head-to-head battle between Farron, a former party president, and Norman Lamb, MP for North Norfolk and a former care minister.

To get on the ballot, a candidate must have the endorsement of 200 members from 20 local party organisations as well as 10% of the parliamentary party, though the latter requirement equates to less than one of the eight remaining Lib Dem MPs. The members will cast their ballots under an alternative vote system and the winner will be announced on 16 July.

Farron, a key figurehead on the left of the Lib Dems, is thought to be the frontrunner owing to his popularity with grassroots activists. He won 52% of the vote in his constituency in the general election and was a vocal opponent of the coalition’s tripling of tuition fees.

Lamb, a former employment lawyer, is more aligned with the politics of the coalition, having served as minister for care and support. He is considered a centrist and served as parliamentary private secretary to Clegg from May 2010 to February 2012.